U.S. patent application number 11/239475 was filed with the patent office on 2007-04-05 for apparatus, system, and method for persistent user-level thread.
This patent application is currently assigned to Intel Corporation. Invention is credited to Anil Aggarwal, Bryant Bigbee, Jason W. Brandt, Gautham Chinya, Richard Hankins, Shivnandan Kaushik, Baiju V. Patel, John L. Reid, Prashant Sethi, John Shen, Hong Wang, Xiang Zou.
Application Number | 20070079301 11/239475 |
Document ID | / |
Family ID | 37887229 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070079301 |
Kind Code |
A1 |
Chinya; Gautham ; et
al. |
April 5, 2007 |
Apparatus, system, and method for persistent user-level thread
Abstract
Embodiments of the invention provide a method of creating, based
on an operating-system-scheduled thread running on an
operating-system-visible sequencer and using an instruction set
extension, a persistent user-level thread to run on an
operating-system-sequestered sequencer independently of context
switch activities on the operating-system-scheduled thread. The
operating-system-scheduled thread and the persistent user-level
thread may share a common virtual address space. Embodiments of the
invention may also provide a method of causing a service thread
running on an additional operating-system-visible sequencer to
provide operating system services to the persistent user-level
thread. Embodiments of the invention may further provide apparatus,
system, and machine-readable medium thereof
Inventors: |
Chinya; Gautham; (Hillsboro,
OR) ; Wang; Hong; (Santa Clara, CA) ; Sethi;
Prashant; (Folsom, CA) ; Kaushik; Shivnandan;
(Portland, OR) ; Bigbee; Bryant; (Scottsdale,
AZ) ; Shen; John; (San Jose, CA) ; Hankins;
Richard; (San Jose, CA) ; Zou; Xiang;
(Portland, OR) ; Patel; Baiju V.; (Portland,
OR) ; Brandt; Jason W.; (Austin, TX) ;
Aggarwal; Anil; (Portland, OR) ; Reid; John L.;
(Portland, OR) |
Correspondence
Address: |
PEARL COHEN ZEDEK LATZER, LLP
1500 BROADWAY, 12TH FLOOR
NEW YORK
NY
10036
US
|
Assignee: |
Intel Corporation
|
Family ID: |
37887229 |
Appl. No.: |
11/239475 |
Filed: |
September 30, 2005 |
Current U.S.
Class: |
717/151 |
Current CPC
Class: |
G06F 9/461 20130101;
G06F 9/3851 20130101; G06F 9/3877 20130101; G06F 9/3009 20130101;
G06F 9/3005 20130101; G06F 9/3861 20130101; G06F 9/3885
20130101 |
Class at
Publication: |
717/151 |
International
Class: |
G06F 9/45 20060101
G06F009/45 |
Claims
1. A method comprising: based on an operating-system-scheduled
thread running on an operating-system-visible sequencer and using
an instruction set extension, creating a persistent user-level
thread to run on an operating-system-sequestered sequencer
independently of context switch activities on the
operating-system-scheduled thread.
2. The method of claim 1, wherein the operating-system-scheduled
thread and the persistent user-level thread share a common virtual
address space.
3. The method of claim 1, comprising suspending running of the
persistent user-level thread when the persistent user-level thread
encounters an event that requires handling by an operating
system.
4. The method of claim 1, comprising causing a service thread
running on an additional operating-system-visible sequencer to
provide operating system services to the suspended persistent
user-level thread.
5. The method of claim 4, wherein the service thread and the
persistent user-level thread run in the context of a same
application.
6. The method of claim 4, wherein providing operating system
services to the persistent user-level thread comprises:
communicating to the additional operating-system-visible sequencer
a control-transfer instruction; and executing the control-transfer
instruction at a privileged level.
7. The method of claim 6, wherein the privileged level includes a
ring-0 level.
8. The method of claim 6, comprising: causing the service thread to
pick up the state of the persistent user-level thread; providing a
proxy execution to the persistent user-level thread; and returning
a post execution state to the persistent user-level thread.
9. The method of claim 8, further comprising resuming running of
the persistent user-level thread from the post execution state
10. An apparatus comprising: a sequencer manager to create, based
on an operating-system-scheduled thread running on an
operating-system-visible sequencer and using an instruction set
extension, a persistent user-level thread to run on an
operating-system-sequestered sequencer independently of context
switch activities on the operating-system-scheduled thread.
11. The apparatus of claim 10, wherein the
operating-system-scheduled thread and the persistent user-level
threads share a common virtual address space.
12. The apparatus of claim 10, wherein the sequencer manager is to
suspend running of the persistent user-level thread when the
persistent user-level thread encounters an event that requires
handling by an operating system.
13. The apparatus of claim 10, wherein the sequencer manager is
adapted to cause a service thread running on an additional
operating-system-visible sequencer to provide operating system
services to the persistent user-level thread.
14. The apparatus of claim 13, wherein the service thread and the
persistent user-level thread run in a context of a same
application.
15. The apparatus of claim 13, wherein the sequencer manager is
adapted to communicate to the additional operating-system-visible
sequencer a control-transfer instruction, and to cause the
control-transfer instruction being executed at a privileged
level.
16. The apparatus of claim 15, wherein the sequencer manager is to
cause the service thread pick up the state of the persistent
user-level thread; to provide a proxy execution to the persistent
user-level thread; and to return a post execution state to the
persistent user-level thread.
17. The apparatus of claim 16, wherein the persistent user-level
thread resumes running from the post execution state.
18. A system comprising: a memory having stored thereon an
operating system, at least one user-level program, an application
program interface to interface the program; and a scheduler to
schedule the execution of the program; a multi-sequencer having at
least one operating-system-visible sequencer and at least one
operating-system-sequestered sequencer; and a sequencer manager to
create, based on an operating-system-scheduled thread running on
the operating-system-visible sequencer and using an instruction set
extension, a persistent user-level thread to run on the
operating-system-sequestered sequencer independently of context
switch activities on the operating system scheduled thread.
19. The system of claim 18, wherein the opetating-system-scheduled
thread and the persistent user-level threads share a common virtual
address space.
20. The system of claim 18, wherein the sequencer manager is to
suspend running of the persistent user-level thread when the
persistent user-level thread encounters an event that requires
handling by an operating system.
21. The system of claim 18, wherein the sequencer manager is
adapted to cause a service thread running on an
operating-system-visible sequencer to provide operating system
services to the persistent user-level thread.
22. The system of claim 21, wherein the sequencer manager is
adapted to communicate to the operating-system-visible sequencer a
control-transfer instruction, and to cause the operating system
visible sequencer to execute the control-transfer instruction at a
privileged level.
23. The system of claim 22, wherein the sequencer manager is to
cause the service thread to pick up the state of the persistent
user-level thread; to provide a proxy execution to the persistent
user-level thread; and to return a post execution state to the
persistent user-level thread.
24. The system of claim 23, wherein the persistent user-level
thread resumes running from the post execution state.
25. A machine-readable medium having stored thereon a set of
instructions that, when executed by a machine, result in creating,
based on an operating-system-scheduled thread running on an
operating-system-visible sequencer and using an instruction set
extension, a persistent user-level thread to run on an
operating-system-sequestered sequencer independently of context
switch activities on the operating-system-scheduled thread.
26. The machine-readable medium of claim 25, wherein the
instructions result in the operating-system-scheduled thread and
the persistent user-level threads to share a common virtual address
space.
27. The machine-readable medium of claim 25, wherein the
instructions result in suspending running of the persistent
user-level thread when the persistent user-level thread encounters
an event that requires handling by an operating system.
28. The machine-readable medium of claim 25, wherein the
instruction result in a service thread running on an additional
operating-system-visible sequencer to provide operating system
services to the persistent user-level thread.
29. The machine-readable medium of claim 28, wherein the
instructions result in communicating to the additional
operating-system-visible sequencer a control-transfer instruction,
and executing the control-transfer instruction at a privileged
level.
Description
BACKGROUND OF THE INVENTION
[0001] In a multi-sequencer computer system or computer platform,
technical as well as economic constraints may justify an asymmetric
organization of specialized computing resources or processors or
processing units. In this application, a processor or processing
unit may also be referred to, hereinafter, as a sequencer or a
processing core.. In general, an operating system may not scale
well on a computer platform having implemented a large number of
sequencers.. In particular, the operating system may not be able to
handle an asymmetric organization of multiple sequencers
efficiently.
[0002] The organization of a computer platform may be asymmetric
with regard to the types of sequencer's that the platform has
implemented. For example, there may be sequencers that are
"visible" to the operating system (OS), referred to herein as
OS-visible sequencers, and are managed by OS kernels. The OS
kernels may be able to control the privilege states of OS-visible
sequencers and to provide exception handlers to process interrupts
and/or exceptions during execution of threads by the OS-visible
sequencers. On the other hand, there may be sequencers that are
"invisible" to the OS, referred to herein as OS-sequestered
sequencers. OS-sequestered sequencers may not execute operating
system codes and may be managed by a sequencer manager.
[0003] Recently, a multi-sequencer
multiple-instruction-flow-multiple-data flow (MIMI)) ISA
(Instruction Set Architecture) extension has been proposed that
defines a set of instructions allowing OS-sequestered sequencers to
be treated as ting-3 user-level architectural resources for
concurrent execution of multiple user-level threads in the single
OS thread context. Therefore, OS-sequestered sequencers become
available to user-level applications. By using the user-level
multi-sequencer MIMI ISA extension, an application thread running
on an OS-visible sequencer may be able to use the additional
sequencers which are sequestered from the OS The multi-sequencer
MIMD ISA extension allows applications to scale, independent of the
OS, for a large number of sequencers by submitting work to
sequencers that may or may not be visible to the operating system.
In the mean time, the operating system may continue to run on a
subset of sequence is that are visible to the OS. The user-level
MIMD ISA extension allows execution of user-level threads to run on
OS-sequestered sequencers, and the user-level threads may run
concurrently with the OS thread that created the user-level threads
and tuns on an OS-visible sequencer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The invention will be understood and appreciated more fully
from the following detailed description of embodiments of the
invention, taken in conjunction with the accompanying drawings of
which:
[0005] FIG. 1 is a block diagram illustration of a multi-sequencer
system according to one illustrative embodiment of the
invention;
[0006] FIG. 2 is a simplified logical view of hardware that forms a
part of a multi-sequencer system according to one illustrative
embodiment of the invention;
[0007] FIG. 3 is a simplified illustration of a multi-sequencer
system able to provide persistent user-level thread services
according to one illustrative embodiment of the invention;
[0008] FIG. 4 is a conceptual illustration of a multi-sequencer
system able to provide persistent user-level thread services
according to one illustrative embodiment of the invention;
[0009] FIG. 5 is an illustrative view of an instruction set
architecture of a multi-sequencer system according to one
illustrative embodiment of the invention;
[0010] FIG. 6 is a simplified illustration of sample instruction
format of a control-transfer instruction according to one
illustrative embodiment of the invention;
[0011] FIG. 7 is a simplified illustration of sample instruction
format of a monitoring instruction according to one illustrative
embodiment of the invention; and
[0012] FIGS. 8 and 9 are simplified flowchart illustrations of the
execution of a persistent user-level thread according to one
illustrative embodiment of the invention
[0013] It will be appreciated that for simplicity and clarity of
illustration, elements shown in the figures have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for
clarity.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0014] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of embodiments of the invention However it will be under stood by
those of ordinary skill in the art that the embodiments of the
invention may be practiced without these specific details. In other
instances, well-known methods and procedures have not been
described in detail so as not to obscure the embodiments of the
invention.
[0015] Some portions of the detailed description in the following
ale presented in terms of algorithms and symbolic representations
of operations on data bits or binary digital signals within a
computer memory. These algorithmic descriptions and representations
may be the techniques used by those skilled in the data processing
arts to convey the substance of the work to others skilled in the
art.
[0016] An algorithm is here, and generally, considered to be a
self-consistent sequence of acts or operations leading to a desired
result. These include physical manipulations of physical
quantities. Usually, though not necessarily, these quantities take
the form of electrical or magnetic signals capable of being stored,
transferred, combined, compared, and otherwise manipulated. It has
proven convenient at times, principally for reasons of common
usage, to refer to these signals as bits, values, elements,
symbols, characters, terms, numbers or the like. It should be
understood, however, that all of these and similar terms are to be
associated with the appropriate physical quantities and are merely
convenient labels applied to these quantities.
[0017] Unless specifically stated otherwise, as apparent from the
following discussions, it is appreciated that throughout the
specification discussions utilizing terms such as "processing",
"computing", "calculating", "determining", or the like, refer to
the action and/or processes of a computer or computing system, or
similar electronic computing device, that manipulate and/or
transform data represented as physical, such as electronic,
quantities within the computing system's registers and/or memories
into other data similarly represented as physical quantities within
the computing system's memories, registers or other such
information storage, transmission or display devices.
[0018] Some embodiments of the invention may be implemented, for
example, using a machine-readable medium or article which may store
an instruction or a set of instructions that, if executed by a
machine, cause the machine to perform a method and/or operations in
accordance with embodiments of the invention Such machine may
include, for example, any suitable processing platform, computing
platform, computing device, processing device, computing system,
processing system, computer, processor, or the like, and may be
implemented using any suitable combination of hardware and/or
software. The machine-readable medium or article may include, for
example, any suitable type of memory unit, memory device, memory
article, memory medium, storage device, storage article, storage
medium and/or storage unit, e.g., memory, removable or
non-removable media, erasable or non-erasable media, writeable or
re-writeable media, digital or analog media, hard disk, floppy
disk, Compact Disk Read Only Memory (CD-ROM), Compact Disk
Recordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk,
magnetic media, various types of Digital Versatile Disks (DVDs), a
tape, a cassette, or the like The instructions may include any
suitable type of code, for, example, source code, target code,
compiled code, interpreted code, executable code, static code,
dynamic code, or the like, and may be implemented using any
suitable high-level, low-level, object-oriented, visual, compiled
and/or interpreted programming language, e.g., C, C++, Java, BASIC,
Pascal, Fortran, Cobol, assembly language, machine code, or the
like.
[0019] Embodiments of the invention may include apparatuses for
performing the operations herein. These apparatuses may be
specially constructed for the desired purposes, or they may include
a general-purpose computer selectively activated or reconfigured by
a computer program stored in the computerd. Such a computer program
may be stored in a computer readable storage medium, such as, but
is not limited to, any type of disk including floppy disks, optical
disks, CD-ROMs, magnetic-optical disks, read-only memories (ROM),
random access memories (RAM), electrically programmable read-only
memories (EPROM), electrically erasable and programmable read only
memories (EEPROM), magnetic or optical cards, or any other type of
media suitable for storing electronic instructions, and capable of
being coupled to a computer system bus.
[0020] The processes and displays presented herein are not
inherently related to any particular computer or other apparatus.
Various general-purpose systems may be used with programs in
accordance with the teachings herein, or it may prove convenient to
construct a more specialized apparatus to perform the desired
method. The desired structure for a variety of these systems will
appear from the description below. In addition, embodiments of the
invention are not described with reference to any particular
programming language. It will be appreciated that a variety of
programming languages may be used to implement the teachings of the
invention as described herein.
[0021] In the following description, various figures, diagrams,
flowcharts, models, and descriptions are presented as different
means to effectively convey and illustrate different embodiments of
the invention that are proposed in this application. It shall be
understood by those skilled in the art that they are provided
merely as illustrative samples, and shall not be constructed as
limiting.
[0022] FIG. 1 is a block diagram illustration of a multi-sequencer
system 100 according to one illustrative embodiment of the
invention.,
[0023] Multi-sequencer system 100, as shown in FIG. 1, may include
a memory 102 and a multi-sequencer hardware 104. Memory 102 may
include, for example, a user-level program 106, a scheduler 108, an
Application Program Interface (API) 110, and an Operating System
(OS) 112. Multi-sequencer hardware 104 may include, for example, a
sequencer manager 114, and a plurality of sequencers, for, example,
sequencers 116, 118, 120 and 122, denoted as sequencers SID0, SID1,
SID2, and SID3, respectively in FIG. 1. Although four sequencers
are shown in FIG. 1, a person skilled in the art may appreciate
that multi-sequencer hardware 104 may have other numbers of
sequencers.
[0024] Sequencer manager 114 may be implemented as a driver, an
extension of an operating system such as an extension of OS 112,
any other hardware or a combination of hardware and software.
Multi-sequencer hardware 104 may be symmetric or asymmetric in
terms of the types of sequencers 116, 118, 120 and/or 122 One or
more of the sequencers 116, 118, 120 and/or 122 may be a physical
processor with its own set of execution resources. Alternatively,
one or more of the sequencers 116, 118, 120 and/or 122 may be a
logical processor (of, for example, a hyper-threaded processor),
that may share physical resources with other logical processors.
Sequencers 116, 118, 120 and 122 may be implemented in a single
hardware core or in multiple separate hardware cores.
[0025] A non-exhaustive list of examples for multi-sequencer system
100 may include a desktop personal computer, a work station, a
server computer, a laptop computer, a notebook computer, a
hand-held computer, a personal digital assistant (PDA), a mobile
telephone, a game console, and the like.
[0026] A non-exhaustive list of examples for memory 102 may include
one or any combination of the following semiconductor devices, such
as synchronous dynamic random access memory (SDRAM) devices, RAMBUS
dynamic random access memory (RDRAM) devices, double data rate
(DDR) memory devices, static random access memory (SRAM) devices,
flash memory (FM) devices, electrically erasable programmable read
only memory (E-EPROM) devices, non-volatile random access memory
(NVRAM) devices, universal serial bus (USB) removable memory
devices, and the like; optical devices, such as compact disk read
only memory (CD ROM), and the like; and magnetic devices, such as a
hard disk, a floppy disk, a magnetic tape, and the like. Memory 102
may be fixed within or removable from system 100.
[0027] According to one illustrative embodiment of the invention,
user-level program 106 may access a thread library via Application
Program Inter face (API) 110 API 110 may provide creation, control,
and synchronization of threads to user-level program 106. Scheduler
108 may schedule instructions of the threads for execution on
multi-sequencer hardware 104.
[0028] A non-exhaustive list of examples for multi-sequencer
hardware 104 may include a plurality of single-threaded or
multi-threaded central processing unit (CPU), digital signal
processor (DSP), reduced instruction set computer (RISC), complex
instruction set computer (CISC) and the like. Moreover,
multi-sequencer 104 may be part of an application specific
integrated circuit (ASIC) or may be a part of an application
specific standard product (ASSP).
[0029] According to one illustrative embodiment of the invention,
multi-sequencer hardware 104 may be a single-core processor having
implemented sequencers 116, 118, 120 and 122 (SID0-SID3) that may
be, for example, logical processors. Single-core processor 104 may
be able to support, for example, concurrent, simultaneous, and/or
switch-on-event multi-threading. According to one illustrative
embodiment, each of the sequencers SID0-SID3 may have its own
next-instruction-pointer logic, while the same single-core
processor 104 may execute all the thread instructions. Each logical
processor SID1-SID3 may maintain its own version of the
architecture state, although execution resources of single-core
processor 104 may be shared among concurrent, simultaneous, and/or
switch-on-event threads.
[0030] While the illustrative embodiment of multi-sequencer
hardware 104 discussed above may refer to single thread per
sequencer, a person skilled in the art shall appreciate that the
application herein is not limited to single-threaded processors.
The techniques discussed herein may equally be employed in any Chip
Multiprocessing (CMP) or Simultaneous Multithreading Processor
(SMP) system, including in a hybrid system with CMP processors and
SMP processors where each core of a CMP processor is a SMP
processor or a Switch-On-Event Multiprocessor (SoeMP). For example,
the techniques disclosed herein may be used in a system that
includes multi-threaded processing cores in a single chip hardware
package 104.
[0031] As is discussed above, sequencers SID0-SID3 are not
necessarily uniform and may be asymmetric with respect to factors
that may affect computation quality such as, for example,
processing speed, processing capability, and power consumption For
example, sequencer SID0 may be a "heavyweight" sequencer in that it
may be designed to process most of the instructions in a given
instruction set architecture (e.g. IA-32 Instruction Set
Architecture associated with a 32-bit processor). Whereas,
sequencer SID1 may be a "lightweight" sequencer in that it may
process a selected subset of those instructions. In another
embodiment of the invention, a heavyweight processor may be one
that processes instructions at a faster late than a lightweight
processor. In addition, some sequencers may be visible and other
sequencers may be invisible to an operating system. For example,
sequencer SID0 may be visible to OS 112, whereas sequencers SID1 to
SID3 may be sequestered from OS 112 However, this does not mean
that heavyweight sequencers are OS-visible and/or lightweight
sequencers are OS-sequestered. An operating system does not
schedule instructions on a sequencer that is in a sequestered state
(such a sequencer is referred to herein as an OS-sequestered
sequencer).
[0032] According to some illustrative embodiments of the invention,
multi-sequencer system 100 may be able to provide services of
persistent user-level threads (PULTs), as detailed below with
reference to FIGS. 2-8. In this application, a regular user-level
thread, or simply referred to hereinafter as user-level thread, may
be a sequence of instructions that contains only non-privileged
instructions that tun in a user-level or ring-3 level. Typically a
user-level thread may be supported "behind the scenes" by an OS
thread, which may also be denoted as native OS thread or just
native thread. In this OS thread context, at least one user-level
thread may run either on an OS-visible sequencer or an
OS-sequestered sequencer. When the OS thread is context switched
out (and in) by the OS, the contexts of all the sequencers
belonging to the OS thread will be saved (and restored).
Accordingly, the user-level threads running on these sequencers
will be suspended (and resumed). According to one embodiment of the
invention, a persistent user-level thread (PULT) is a user-level
thread that runs on an OS-sequestered sequencer. The PULT may be
executed in an environment, for example, a virtual address space
(VAS) of another user-level thread that creates the PULT. The
execution of the PULT may be independent of, and therefore not in
synchronous with, the execution of the user-level thread that
creates the PULT Even when the OS thread to which the user-level
thread belongs is context switched out, the PULT may continue
execution on the OS-sequestered sequencer. This is referred to
herein by the notion of "persistence"--continued execution of the
user-level thread irrespective of the OS thread context switch
activities on the thread that spawned or created the PULT.
[0033] FIG. 2 is a simplified logical view of hardware 200 that
forms a part of a multi-sequencer system according to one
illustrative embodiment of the invention.
[0034] Hardware 200 may correspond to multi-sequencer hardware 104
that forms a part of multi-sequencer system 100 in FIG. 1.
Multi-sequencer hardware 104 may include sequencer manager 114 and,
for example, a plurality of sequencers 116, 118, 120 and 122 as
shown in FIG. 1. According to one embodiment of the invention,
sequencer manager 114 may be able to virtualize sequencers 116,
118, 120 and 122 in such away that sequencers 116, 118, 120 and 122
appear-to user-level program 106 as uniform and symmetric. In other
words, sequencer manager 201, which corresponds to sequencer
manager 114 in FIG. 1, may mask the asymmetry of sequencers 211,
212, 213 and 214 so that from a logical point of view of an
assembly language programmer sequencers 211, 212, 213 and 214 may
look uniform and symmetric, as in FIG. 2, and symbolized by their
squares of equal size Sequencers 211, 212, 213 and 214 may
represent logical processors SID0, SID1, SID2 and SID3 in FIG.
1.
[0035] FIG. 3 is a simplified illustration of a multi-sequencer
system 300 able to provide persistent user-level thread services
according to one illustrative embodiment of the invention.
[0036] According to one embodiment of the invention, execution of
an application 301, which may be, for example, user-level program
106 of FIG. 1 may be managed by an operating system (OS) 302. OS
302 may handle execution of application 301 by creating and
scheduling one or more native threads, each potentially including
user-level threads, such as for example a native thread 303 in FIG.
3 which run on one of a set of sequencers that are visible to OS
302, for example, sequencers 311 and 312. OS 302 may manage
sequencers 311 and 312 through one or more of its OS kernels. OS
302 may also control the privilege states of sequencers 311 and 312
and be responsible for handling interrupts and exceptions that may
occur on sequencers 311 and 312.
[0037] According to one embodiment of the invention, a sequencer
manager 310 may have control access to both sequencers 311 and 312
that are OS-visible, and another set of sequencers, for example,
sequencers 313, 314, 315, 316, 317 and 318 that are sequestered
from OS 302 and not managed by the kernels of OS 302. Sequencers
313, 314, 315, 316, 317 and 318 are OS-sequestered, or
"OS-invisible", sequencers.
[0038] According to one embodiment of the invention, an
OS-scheduled thread, (e.g., a native thread that potentially
includes a user-level thread) may interact with sequencer manager
310 through an interface that may be provided through hardware or
software or a combination of both. In order to use sequencers that
are not visible to OS 302, such as sequencers 313, 314, 315, 316,
317 and 318, an OS-scheduled thread, for example the native thread
303, may send a request to sequencer manager 310 to create a
user-level thread, for example, thread 304, to tun on one of the
OS-sequestered sequencers, for example, sequencer 313. According to
one embodiment of the invention, user-level thread 304 may run on
sequencer 313 independent of the OS context switch activities of
the native thread 303 and therefore may be a persistent user-level
thread (PULT).
[0039] In the following description, native thread 303 is used as
an example to illustrate the creation and execution of a persistent
user -level thread. A person skilled in the art will appreciate
that following description also applies to other threads such as,
for example a user level thread that belongs to a native
thread.
[0040] According to one illustrative embodiment of the invention,
OS-sequestered sequencer 313 may execute PULT 304 in a virtual
address space (VAS) 320 that is shared by user-level thread 303
running on OS-visible sequencer 311. OS 302 may create VAS 320 for
the execution of application 301. According to one illustrative
embodiment of the invention, by sharing a common VAS 320, sequencer
manager 310 may be able to capture an execution environment, for
example, a virtual address map, of user-level thread 303 that runs
on OS-visible sequencer 311, and then apply this execution
environment to PULT 304 that runs on OS-sequestered sequencer 313.
According to one embodiment of the invention, OS-sequestered
sequencer 313 may have one or more snoopy TLB's (Translation
Lookaside Buffer) that are able to automatically track future
changes in the virtual address space. A TLB may be a small cache
present in a processor that keeps track of virtual to physical
address translation for quick lookup. A processor may use this TLB
to avoid unnecessary page walks to translate virtual address to
physical address.
[0041] FIG. 4 is a conceptual illustration of a multi-sequencer
system 400 able to provide persistent user-level thread services
according to one illustrative embodiment of the invention.
[0042] According to one embodiment of the invention,
multi-sequencer system 400 may include a sequencer manager 410 that
manages a plurality of OS-sequestered sequencers, for example,
sequencers 411, 412, 413 and 414, and other OS-visible sequencers,
for example, sequencers 405 and 406. An operating system (OS) 402
may manage execution of one or mote user-level applications, for
example, applications 401A and 401B. OS 402 manages applications
401A and 401B by creating one or more threads including, for
example, user-level threads 403 and 404, which run on OS-visible
sequencers 405 and 406, and other native threads.
[0043] Sequencer manager 410 may provide execution resources to
applications 401A and 401B through access to sequencers 411, 412,
413 and 414, which are sequestered from OS 402 and not managed by
OS 402. The access may be provided through requests made by threads
40.3 and 404 running on OS-visible sequencers 405 and 406 or other
native threads scheduled by the OS. As a result, applications 401A
and 401B may have access to OS-sequestered sequencers 411, 412, 413
and 414 via user-level threads 403 and/or 404 or other native
threads.
[0044] According to one embodiment of the invention, sequencer
manager 410 may allocate various time slots on sequencers 411, 412,
413 and 414 for execution of one or more persistent user-level
threads created by user-level threads 403 and 404 for applications
401A and 401B. For example, symbols t.sub.1, t.sub.2, t.sub.3,
t.sub.4, t.sub.5 and t.sub.6 in FIG. 4 may denote the time slots
that are assigned for the execution of PULTs T.sub.1, T.sub.2,
T.sub.3, T.sub.4, T.sub.5 and T.sub.6, respectively.
[0045] According to one embodiment of the invention, sequencer
manager 410 may set up one or more interrupt descriptor tables, for
example, tables 421, 422, 423 and 424, for one or more
OS-sequestered sequencers, for example, sequencers 411, 412, 413
and 414. An interrupt descriptor table, for example, table 421, may
include an event handler 431 to handle events occurring on
sequencer 411. During execution time, for example, t.sub.3 of PULT
13 on an OS-sequestered sequencer, for example, sequencer 411, PULT
T.sub.3 may encounter an event or situation such as, for example, a
page fault or a system call, that requires handling or attention of
OS 402. Event handler 431 may then suspend the execution of PULT
T.sub.3 and save the execution state, at the time the event
happens, of PULT T.sub.3.
[0046] According to another embodiment of the invention, an
OS-invisible sequencer, for example, sequencer 411 may directly
interrupt the execution of an OS-visible sequencer, for example,
sequencer 405 that invoked the PULT T.sub.3, when encountering a
page fault or a system call. Sequencer 411 may then send a trigger
to sequencer manager 410 requesting handling of the interruption.
According to yet another embodiment of the invention,
OS-sequestered sequencer 411 may program a ring-0 service channel
or channel to handle a page fault or system call. A channel may be
a register holding architectural state that includes, for example,
a trigger-response mapping where the trigger is an architecturally
defined set of one or more processor conditions and the response is
a service routine. In addition, a channel may be programmed, for
example, by a user-level instruction. When the page fault or system
call occurs, OS-sequestered sequencer- 411 may invoke a handler
whose address is specified in the channel.
[0047] PULT T.sub.3 may remain suspended until a time when a new
user-level thread, for example, thread 409, which runs the same
application 401A, is scheduled to run on an OS-visible sequencer.
Thread 409, also referred to as a service thread, may make a
request to sequencer manager 410 to confirm or verify whether there
are any PULTs that have been suspended and are waiting for OS
services which may be provided, for example, through a proxy
execution as described below in detail. A proxy execution may be
performed through thread 409 impersonating or imitating PULT
T.sub.3, by picking up the state of PULT T.sub.3 from sequencer
manager 410. The execution state of PULT T.sub.3 may be resumed by
service thread 409 which shares a common address space, for
example, a commonly shared virtual address space (VAS) (FIG. 3)
Thread 409 may then service the execution condition that has caused
the suspension of PULT T.sub.3. After the service, thread 409 may
proceed to save the post-execution state and return the state to
sequencer manager 410. Sequencer manager 410 may subsequently pass
the state to PULT T.sub.3 to resume its execution.
[0048] The proxy execution discussed above may create an illusion
of'symmetry to an application programmer and therefore hide the
inherent asymmetric nature of how a multi-sequencer system, for
example, system 100, is built.
[0049] FIG. 5 is an illustrative view of an Instruction Set
Architecture (ISA) 500 of a multi-sequencer system according to one
illustrative embodiment of the invention.
[0050] An ISA defines a logical view of a system as seen by an
assembly language programmer, binary translator, assembler or the
like. ISA 500 may include a logical storage 502 and an instruction
set 504. Logical storage 502 may define a visible memory hierarchy,
addressing scheme, register set, etc for a multi-sequencer system
such as, for example, multi-sequencer system 100 as in FIG. 1,
whereas instruction set 504 may define the instructions and the
format of the instructions that multi-sequencer system 100 may
support.
[0051] Instruction set 504 may include the instruction set known as
IA-32 instruction set and, according to illustrative embodiments of
the invention, its extension although the present invention is not
limited in this respect and other instruction sets are possible.
According to one embodiment of the invention, instruction set 504
may include, for example, an E-SXFR instruction that includes a
SXFR control-transfei instruction and its extension, and an
E-SEMONITOR instruction that includes a SEMONITOR monitoring
instruction and its extension. Compared to SXFR and SEMONITOR,
which can be performed between two sequencers belonging to the same
OS native thread, E-SXFR and E-SEMONITOR can be performed between
two sequencers that belong to two distinct OS native threads
respectively, which may run at different privilege levels. For
example, one thread may be a user-level application that is subject
to OS context switch, and the other thread may be a PULT that runs
persistently in the privilege level, like a device driver, and is
not subject to OS context switch.
[0052] According to one embodiments of the invention, the E-SXFR
instruction may be used to send a signal from a fist sequencer to a
second sequencer, and the E-SEMONITOR instruction may be used to
configure the second sequencer to monitor for signals coming from
the first sequencer. Furthermore, the E-SXFR control transfer and
E-MONITOR monitoring instructions are sequencer aware, and may be
used to construct other sequencer aware composite instructions.
[0053] According to one embodiment of the invention, an E-SXFR
instruction may have a sample instruction format as shown in FIG.,
6, It is shown, in FIG. 6, that the E-SXFR instruction may include
an Opcode 602, and operands 604, 606, 608, 610 and 612. According
to one embodiment of the invention, a sequencer manager may provide
an E-SXFR instruction with operands, which may include the
privilege state of a sequencer, such as to create an execution
environment to service suspended persistent user-level threads.
[0054] According to one embodiment, operand 604 may correspond to a
sequencer ID (SID) for a destination/target sequencer to which the
E-SXFR instruction signal is sent. Operand 606 may include a
scenario or control message, which may be an architecturally
defined identifier code representing a condition or anticipated
event. A scenario may be used to affect asynchronous control
transfer as described in detail with reference to TABLE 1.
[0055] According to one embodiment, operand 608 may include a
parameter that conditions the execution of instructions on a
sequencer that executes the E-SXFR instruction. Examples of
parameters, as shown in FIG. 6 as conditional parameter, may
include a "WAIT" or "NO-WAIT" parameter. For example, when an
E-SXFR instruction is used in a proxy execution scenario, the WAIT
conditional parameter may cause the execution of instructions on a
sequencer that executes the E-SXFR instruction to stop, pending
completion of proxy execution on another sequencer. The NO-WAIT
conditional parameter may specify that execution on a sequencer
that executes the E-SXFR instruction may continue in parallel with
proxy execution on another instruction sequencer.
[0056] According to one embodiment, operand 610 may include a
scenario-specific payload or data message. For example, in the case
of a FORK scenario, the payload may include an instruction pointer
at which execution on the sequencer identified by operand 604 is to
commence. According to another embodiment, payload operand 610 may
include an instruction pointer, a stack pointer, a set of control
registers, etc. Addresses contained in payload operand 610 may be
expressed in a variety of addressing modes such as, for example,
literal, register indirect, and/or base/offset addressing.
[0057] According to one embodiment, operand 612 may specify a
Touting method or function on the SID contained in operand 604. The
touting function controls whether the signal, which is created as a
result of executing the E-SXFR instruction, is sent as a broadcast,
a unicast, or a multicast signal. The touting function may also
encode information such as, for example, topology-specific hint
that may be used to assist an underlying inter-sequencer
interconnect in routing to deliver the signal.
[0058] According to one embodiment, the E-SEMONITOR instruction may
have a sample instruction format as shown in FIG. 7. It is shown,
in FIG. 7, that the E-SEMONITOR instruction may include an Opcode
702, and operands 704, 706 and 708. Operands 704, 706 and 708 may
include information of the privilege state of sequencer to help
create an execution environment for a persistent user-level thread.
For example, operand 704 may specify a scenario by including a
scenario ID. Operand 706 may include information related to a
sequencer ID (SID) and an instruction pointer (EIP). For
descriptive convenience, information contained in operand 706 may
be referred to herein as a "SIDEIP", as shown in FIG. 7.
[0059] The E-SEMONIIOR instruction may map a scenario specified in
operand 704 to a SIDEIP specified in operand 706. Mapping of a
scenario to a SIDEIP may be referred to herein as mapping of a
"service channel". Operand 708 may allow a programmer to enter one
or more control parameters to specify or control how a particular
service channel is to be serviced. For example, a programmer may
use the E-SEMONITOR instruction to program the service channels
that a sequencer may monitor.
[0060] Based on the above description, it will be appreciated that
both the E-SXFR and E-SEMONITOR instructions are "sequencer-aware"
instructions in that they include operands that may identify
particular sequencers.
[0061] FIGS. 8 and 9 ale simplified flowchart illustrations of the
execution of a persistent user-level thread according to some
illustrative embodiments of the invention. The same block numbers
are used to indicate the same operation.
[0062] According to one embodiment of the invention, an
OS-sequestered sequencer 822 may execute a persistent user-level
thread as indicated at block 801. The persistent user-level thread
may be referred to herein as PULT-1 for convenience of description.
PULT-1 may be created, for example, by a first user-level thread
that is executed by a first OS-visible sequencer. During execution,
PULT-1 may encounter one or more events that require services or
attention of an OS. A second user-level thread, which may or may
not be the same user-level thread as the first user-level thread
that created PULT-1 and execute on a second OS-visible sequencer
for example OS-visible sequencer 821, may provide the requested OS
services to PULT-1 as described below in detail.
[0063] According to one embodiment of the invention, PULT-1 may
encounter an event at time t.sub.1 requiring OS services, as
indicated at block 802 in FIGS. 8 and 9. Upon detection f the
event, a sequencer manager 820 may invoke a procedure to save the
state of PULT-1 at time t.sub.1, as indicated at block 803, such as
a logic pointer, for example. The execution of PULT-1 may then be
suspended from time t.sub.2 and onward as indicated at block 804,
after the state of PULT-1 has been saved as indicated at block 803.
According to one embodiment of the invention, the execution of
PULT-1 may also be suspended by sequencer manager 820, through an
external interruption, after receiving a notification about an
event that requires operating system services. PULT-1 may remain
suspended until the requested OS services ate provided through, for
example, proxy execution by a service thread.
[0064] According to one illustrative embodiment of the invention,
at some point of time, an OS-scheduled thread such as a new
user-level thread may start to fun on OS-visible sequencer 821 as
indicated at block 805. This new user-level thread may be executed
for the same application as PULT-1 This thread may be able to
provide OS services through, for example, proxy execution, to
PULT-I and therefore may be referred to herein as a service thread.
Before providing OS services, the service thread may check or
verify with sequencer manager 820, as indicated at block 806,
whether there are any suspended PULTs that are waiting for OS
services.
[0065] The service thread may identify PULT-1 as a thread waiting
for OS services. According to one embodiment of the invention, the
service thread may then proceed to imitate, in other words,
impersonate, PULT-1 by picking up the execution state of PULT-1
through, for example, their commonly shared virtual address space
(VAS) as indicated at block 807. PULT-1, imitated by the service
thread, may then get executed on the OS-visible sequencer executing
the service thread to receive OS services. As a result, OS services
are provided to PULT-1, as indicated at block 808, through proxy
execution of the service thread and the condition under which
PULT-1 was suspended is now serviced by the operating system.
According to one embodiment of the invention, a user level thread
that runs on an OS-visible sequencer, for example, OS-visible
sequencer 821, may detect a suspended PULT by monitoring an address
location using an scenario. A service scenario is a condition that
may be used to monitor, for example, cache misses, and if a cache
miss occurs which causes, for example, a threshold being crossed, a
handler in the service channel may be invoked.
[0066] According to one embodiment of the invention, after the
operating system completes servicing the condition of the suspended
PULT-1, the post-execution state of PULT-1 may be saved and
subsequently returned to OS-sequestered sequencer 822 through
sequencer manager 820 as indicated at block 809. After receiving
the post execution state from the service thread, OS-sequestered
sequencer. 822 may resume its execution of PULT-1 as indicated at
block 810.
[0067] Table 1 contains a list of sample scenarios according to
some illustrative embodiments of the invention. TABLE-US-00001
TABLE 1 SPU Characteristics Egress Service Scenarios Ingress
Service Scenarios OS OS- Operations that require OS Incoming
control messages Visibility invisible handling and cause cross
Go_shred ring-level transitions, e.g. Halt_shred Page fault
handling Report/Self I/O access Save/Restore_shred
Single-step_shred OS- Outgoing control messages Operations that
require OS visible Fork handling and cause cross Join ring-level
transitions, e.g. Yield Page fault handling Wait I/O access
Scatter/Set Gather/Get CSAVE/RSTOR Go/Halt/Single-step Core Simple
SSE13 instruction Complexity Complex SSE13 execution
[0068] According to illustrative embodiments of the invention,
scenarios in Table 1 may be divided into egress services and
ingress services. Among each service, operations and control
messages may be characterized by their OS-visibility which may be
part of the characteristics of a shred processing unit (SPU). Among
egress services, there are scenarios of operations that fall into
the category of resource not available (RNA), which is a category
for events generated during execution on a sequencer due to access
to a resource not being available on an OS-sequestered sequencer.
According to one embodiment of the invention, scenarios that fall
into the category of RNA may include, for example, page fault
handling and/or I/O access on the OS-sequestered sequencer which is
incapable of directly activating OS service.
[0069] According to illustrative embodiments of the invention,
accompanying these scenarios of operations described above is a set
of outgoing control messages. In one illustrative embodiment, the
messages may include, for example, the messages as listed under
egress service scenarios in Table 1. However, the invention is not
limited in this respect and other messages may be used. The control
messages go to one or more OS-visible sequencers.
[0070] In relation to the egress service scenarios discussed above,
there are ingress service scenarios that fall into the category of
an OS-visible sequencer providing resource to service requests from
an OS-sequestered sequencer. As is shown in Table 1 under ingress
service scenarios, these services correspond directly to the
scenarios under egress service but are available from OS-visible
sequencers In one illustrative embodiment, the incoming control
messages, accompanying the ingress services, may include the
messages as listed under ingress service scenarios in Table 1
However, the invention is not limited in this respect and other
messages may be used The incoming messages may come from one or
more OS-sequestered sequencers.
[0071] According to illustrative embodiments of the invention,
instructions that serve the egress services are, for example,
relatively simple SSE13 instructions in terms of core complexity,
and instructions that serve, for example, the ingress services or
requests from an OS-sequestered sequencer are, in general, more
complex.
[0072] While certain features of the invention have been
illustrated and described herein, many modifications,
substitutions, changes, and equivalents will now occur to those of
ordinary skill in the art. It is, therefore, to be understood that
the appended claims are intended to cover all such modifications
and changes as fall within the spirit of the invention.
* * * * *